The present invention refers to lightweight, heat insulated roof structures, suitable for workshops, indoor arenas and other non-residential buildings.
For many years roof structures have included a carrying structure of plate material, mostly corrugated sheet metal, which were supported by rafters. Heat insulating material was bonded to the plate structure, and on top of the insulating material several layers of watertight, asphalted-felt, or the like, were spread out. Roofs of this type have not been satisfactory, as the watertight covering often cracks due to age incidents of the asphalt material. The covering is futhermore sensitive to workmen walking thereon, as well as to movements and sinkings in the building structure. Temperature changes may cause ruptures, and the fire-spreading capacity of asphalted felt makes the structure unfavourable from a fire resisting point of view.
A further drawback is that the corrugated plate often has to be mounted so the flutes thereof run transversely to the inclination of the roof. Water from leaks, or condensation, will then collect in the flutes, and the damage is often not discovered until the corrosion is destructive.
During later years the asphalt-felt to some extent has been substituted by metal sheeting. Distance members, such as purlins, have been fitted between a lower layer of boards or plates and the metal sheeting to form spaces for insulating material, such as slates of mineral wool. Roofs for workshops and the like often have a rather big span, and it is desirable to locate the primary carrying structures (the rafters) widely apart. It is therefore important, that the roof structure has a low dead weight. Earlier roof designs have had a rather high dead weight, as mineral wool of high density and/or twin, continuous layers of sheet material have been included.
A further embodiment of roof design is the purlin roof. This includes purlins (or light beams), which are located transversely in relation to the rafters. Plate material, usually corrugated sheet metal or metal bands, is fitted with the flutes, or the folds, running parallel to the inclination of the roof. Such a roof will require a minimum of maintenance and is not noticeably influenced by movements in the building. No rational heat insulation of this type of roofs has, however, hitherto been proposed, and it has mostly been used for sheds, where a slight anti-condensing insulation has been satisfactory.
One aim of the present invention is to propose a light roof structure having fine heat insulation properties, which has good fire resistant properties, and has a low dead weight, in which a continuous diffusion barrier effectively prevents the formation of condensate, and where the heat insulation material may be arranged so it forms a noise absorbent.
An other object of the invention is to propose a supporting structure for the insulation, which is easily fitted to match varying demands in insulating thicknesses.
A further object of the invention is to provide a foraminous supporting structure, permitting a lower insulating layer to act as a sound absorbent.
An other object of the invention is to provide means for stabilizing the purlins.
A further object is to arrange the supporting structure so it will act as a safety net for the workmen installing the roof.
Still another object of the invention is to arrange the components so as to make pre-assembling on the ground easier.